[PATCH v3 2/3] vinyl: abort affected transactions when space is removed from cache

[Vladimir Davydov <vdavydov.dev@gmail.com>]

A DDL operation creates a new struct space container, moving unaffected
indexes from the old container, then destroying it. The problem is there
may be a DML request for this space, which was passed the old container
in the argument list and then yielded on disk read. When it resumes, it
may try to dereference the old space container, which may have already
been destroyed. This will most certainly result in a crash.

To address this problem, we introduce a new space callback, invalidate,
which is called for the old space on space_cache_replace(). In case of
vinyl, this callback aborts all transactions involving the space. To
prevent a DML request from dereferencing a destroyed space, we also make
the iterator code check the current transaction state after each yield
and return an error if it was aborted. This should make any DML request
bail out early without dereferencing the space anymore.

Closes #3420
---
 src/box/blackhole.c            |   1 +
 src/box/memtx_space.c          |   1 +
 src/box/schema.cc              |   3 ++
 src/box/space.c                |   6 +++
 src/box/space.h                |  15 ++++++
 src/box/sysview.c              |   1 +
 src/box/vinyl.c                |  21 ++++++++
 src/box/vy_point_lookup.c      |  14 ++++++
 src/box/vy_read_iterator.c     |  13 +++++
 test/vinyl/errinj_ddl.result   | 110 +++++++++++++++++++++++++++++++++++++++++
 test/vinyl/errinj_ddl.test.lua |  51 +++++++++++++++++++
 11 files changed, 236 insertions(+)

diff --git a/src/box/blackhole.c b/src/box/blackhole.c
index 95064e1f..b69e543a 100644
--- a/src/box/blackhole.c
+++ b/src/box/blackhole.c
@@ -129,6 +129,7 @@ static const struct space_vtab blackhole_space_vtab = {
 	/* .build_index = */ generic_space_build_index,
 	/* .swap_index = */ generic_space_swap_index,
 	/* .prepare_alter = */ generic_space_prepare_alter,
+	/* .invalidate = */ generic_space_invalidate,
 };
 
 static void
diff --git a/src/box/memtx_space.c b/src/box/memtx_space.c
index 92ec0b30..d8529fe0 100644
--- a/src/box/memtx_space.c
+++ b/src/box/memtx_space.c
@@ -961,6 +961,7 @@ static const struct space_vtab memtx_space_vtab = {
 	/* .build_index = */ memtx_space_build_index,
 	/* .swap_index = */ generic_space_swap_index,
 	/* .prepare_alter = */ memtx_space_prepare_alter,
+	/* .invalidate = */ generic_space_invalidate,
 };
 
 struct space *
diff --git a/src/box/schema.cc b/src/box/schema.cc
index 9e3f5561..79d0de4e 100644
--- a/src/box/schema.cc
+++ b/src/box/schema.cc
@@ -257,6 +257,9 @@ space_cache_replace(struct space *old_space, struct space *new_space)
 		diag_log();
 		panic("Can't update space cache");
 	}
+
+	if (old_space != NULL)
+		space_invalidate(old_space);
 }
 
 /** A wrapper around space_new() for data dictionary spaces. */
diff --git a/src/box/space.c b/src/box/space.c
index e140f3d5..1379fa34 100644
--- a/src/box/space.c
+++ b/src/box/space.c
@@ -637,4 +637,10 @@ generic_space_prepare_alter(struct space *old_space, struct space *new_space)
 	return 0;
 }
 
+void
+generic_space_invalidate(struct space *space)
+{
+	(void)space;
+}
+
 /* }}} */
diff --git a/src/box/space.h b/src/box/space.h
index 211706d2..bbb2addd 100644
--- a/src/box/space.h
+++ b/src/box/space.h
@@ -133,6 +133,14 @@ struct space_vtab {
 	 */
 	int (*prepare_alter)(struct space *old_space,
 			     struct space *new_space);
+	/**
+	 * Called right after removing a space from the cache.
+	 * The engine should abort all transactions involving
+	 * the space, because the space will be destroyed soon.
+	 *
+	 * This function isn't allowed to yield or fail.
+	 */
+	void (*invalidate)(struct space *space);
 };
 
 struct space {
@@ -407,6 +415,12 @@ space_prepare_alter(struct space *old_space, struct space *new_space)
 	return new_space->vtab->prepare_alter(old_space, new_space);
 }
 
+static inline void
+space_invalidate(struct space *space)
+{
+	return space->vtab->invalidate(space);
+}
+
 static inline bool
 space_is_memtx(struct space *space) { return space->engine->id == 0; }
 
@@ -469,6 +483,7 @@ int generic_space_check_format(struct space *, struct tuple_format *);
 int generic_space_build_index(struct space *, struct index *,
 			      struct tuple_format *);
 int generic_space_prepare_alter(struct space *, struct space *);
+void generic_space_invalidate(struct space *);
 
 #if defined(__cplusplus)
 } /* extern "C" */
diff --git a/src/box/sysview.c b/src/box/sysview.c
index 63b669d0..f9edd2d0 100644
--- a/src/box/sysview.c
+++ b/src/box/sysview.c
@@ -495,6 +495,7 @@ static const struct space_vtab sysview_space_vtab = {
 	/* .build_index = */ generic_space_build_index,
 	/* .swap_index = */ generic_space_swap_index,
 	/* .prepare_alter = */ generic_space_prepare_alter,
+	/* .invalidate = */ generic_space_invalidate,
 };
 
 static void
diff --git a/src/box/vinyl.c b/src/box/vinyl.c
index a6a5f187..da891025 100644
--- a/src/box/vinyl.c
+++ b/src/box/vinyl.c
@@ -1031,6 +1031,26 @@ vinyl_space_prepare_alter(struct space *old_space, struct space *new_space)
 	return 0;
 }
 
+static void
+vinyl_space_invalidate(struct space *space)
+{
+	struct vy_env *env = vy_env(space->engine);
+	/*
+	 * Abort all transactions involving the invalidated space.
+	 * An aborted transaction doesn't allow any DML/DQL requests
+	 * so the space won't be used anymore and can be safely
+	 * destroyed.
+	 *
+	 * There's a subtle corner case though - a transaction can
+	 * be reading disk from a DML request right now, with this
+	 * space passed to it in the argument list. However, it's
+	 * handled as well: the iterator will return an error as
+	 * soon as it's done reading disk, which will make the DML
+	 * request bail out early, without dereferencing the space.
+	 */
+	tx_manager_abort_writers_for_ddl(env->xm, space);
+}
+
 /**
  * This function is called after installing on_replace trigger
  * used for propagating changes done during DDL. It aborts all
@@ -4543,6 +4563,7 @@ static const struct space_vtab vinyl_space_vtab = {
 	/* .build_index = */ vinyl_space_build_index,
 	/* .swap_index = */ vinyl_space_swap_index,
 	/* .prepare_alter = */ vinyl_space_prepare_alter,
+	/* .invalidate = */ vinyl_space_invalidate,
 };
 
 static const struct index_vtab vinyl_index_vtab = {
diff --git a/src/box/vy_point_lookup.c b/src/box/vy_point_lookup.c
index 9f7796eb..9e1f3ca7 100644
--- a/src/box/vy_point_lookup.c
+++ b/src/box/vy_point_lookup.c
@@ -198,6 +198,7 @@ vy_point_lookup(struct vy_lsm *lsm, struct vy_tx *tx,
 {
 	/* All key parts must be set for a point lookup. */
 	assert(vy_stmt_is_full_key(key, lsm->cmp_def));
+	assert(tx == NULL || tx->state == VINYL_TX_READY);
 
 	*ret = NULL;
 	double start_time = ev_monotonic_now(loop());
@@ -239,6 +240,19 @@ restart:
 		errinj(ERRINJ_VY_POINT_ITER_WAIT, ERRINJ_BOOL)->bparam = false;
 	});
 
+	if (tx != NULL && tx->state == VINYL_TX_ABORT) {
+		/*
+		 * The transaction was aborted while we were reading
+		 * disk. We must stop now and return an error as this
+		 * function could be called by a DML request aborted
+		 * by a DDL operation: failing early will prevent it
+		 * from dereferencing a destroyed space.
+		 */
+		diag_set(ClientError, ER_TRANSACTION_CONFLICT);
+		rc = -1;
+		goto done;
+	}
+
 	if (mem_list_version != lsm->mem_list_version) {
 		/*
 		 * Mem list was changed during yield. This could be rotation
diff --git a/src/box/vy_read_iterator.c b/src/box/vy_read_iterator.c
index 2864a280..60c43555 100644
--- a/src/box/vy_read_iterator.c
+++ b/src/box/vy_read_iterator.c
@@ -501,6 +501,17 @@ rescan_disk:
 	}
 	vy_read_iterator_unpin_slices(itr);
 	/*
+	 * The transaction could have been aborted while we were
+	 * reading disk. We must stop now and return an error as
+	 * this function could be called by a DML request that
+	 * was aborted by a DDL operation: failing will prevent
+	 * it from dereferencing a destroyed space.
+	 */
+	if (itr->tx != NULL && itr->tx->state == VINYL_TX_ABORT) {
+		diag_set(ClientError, ER_TRANSACTION_CONFLICT);
+		return -1;
+	}
+	/*
 	 * The list of in-memory indexes and/or the range tree could
 	 * have been modified by dump/compaction while we were fetching
 	 * data from disk. Restart the iterator if this is the case.
@@ -842,6 +853,8 @@ vy_read_iterator_track_read(struct vy_read_iterator *itr, struct tuple *stmt)
 NODISCARD int
 vy_read_iterator_next(struct vy_read_iterator *itr, struct tuple **result)
 {
+	assert(itr->tx == NULL || itr->tx->state == VINYL_TX_READY);
+
 	ev_tstamp start_time = ev_monotonic_now(loop());
 
 	struct vy_lsm *lsm = itr->lsm;
diff --git a/test/vinyl/errinj_ddl.result b/test/vinyl/errinj_ddl.result
index 04cb581f..794125e8 100644
--- a/test/vinyl/errinj_ddl.result
+++ b/test/vinyl/errinj_ddl.result
@@ -682,3 +682,113 @@ box.commit()
 s:drop()
 ---
 ...
+--
+-- gh-3420: crash if DML races with DDL.
+--
+fiber = require('fiber')
+---
+...
+-- turn off cache for error injection to work
+default_vinyl_cache = box.cfg.vinyl_cache
+---
+...
+box.cfg{vinyl_cache = 0}
+---
+...
+s = box.schema.space.create('test', {engine = 'vinyl'})
+---
+...
+_ = s:create_index('i1')
+---
+...
+_ = s:create_index('i2', {parts = {2, 'unsigned'}})
+---
+...
+_ = s:create_index('i3', {parts = {3, 'unsigned'}})
+---
+...
+_ = s:create_index('i4', {parts = {4, 'unsigned'}})
+---
+...
+for i = 1, 5 do s:replace({i, i, i, i}) end
+---
+...
+box.snapshot()
+---
+- ok
+...
+test_run:cmd("setopt delimiter ';'")
+---
+- true
+...
+function async(f)
+    local ch = fiber.channel(1)
+    fiber.create(function()
+        local _, res = pcall(f)
+        ch:put(res)
+    end)
+    return ch
+end;
+---
+...
+test_run:cmd("setopt delimiter ''");
+---
+- true
+...
+-- Issue a few DML requests that require reading disk.
+-- Stall disk reads.
+errinj.set('ERRINJ_VY_READ_PAGE_TIMEOUT', 0.01)
+---
+- ok
+...
+ch1 = async(function() s:insert({1, 1, 1, 1}) end)
+---
+...
+ch2 = async(function() s:replace({2, 3, 2, 3}) end)
+---
+...
+ch3 = async(function() s:update({3}, {{'+', 4, 1}}) end)
+---
+...
+ch4 = async(function() s:upsert({5, 5, 5, 5}, {{'+', 4, 1}}) end)
+---
+...
+-- Execute a DDL operation on the space.
+s.index.i4:drop()
+---
+...
+-- Resume the DML requests. Check that they have been aborted.
+errinj.set('ERRINJ_VY_READ_PAGE_TIMEOUT', 0)
+---
+- ok
+...
+ch1:get()
+---
+- Transaction has been aborted by conflict
+...
+ch2:get()
+---
+- Transaction has been aborted by conflict
+...
+ch3:get()
+---
+- Transaction has been aborted by conflict
+...
+ch4:get()
+---
+- Transaction has been aborted by conflict
+...
+s:select()
+---
+- - [1, 1, 1, 1]
+  - [2, 2, 2, 2]
+  - [3, 3, 3, 3]
+  - [4, 4, 4, 4]
+  - [5, 5, 5, 5]
+...
+s:drop()
+---
+...
+box.cfg{vinyl_cache = default_vinyl_cache}
+---
+...
diff --git a/test/vinyl/errinj_ddl.test.lua b/test/vinyl/errinj_ddl.test.lua
index 50dc4aa1..84f33277 100644
--- a/test/vinyl/errinj_ddl.test.lua
+++ b/test/vinyl/errinj_ddl.test.lua
@@ -298,3 +298,54 @@ s:replace{1, 3}
 box.commit()
 
 s:drop()
+
+--
+-- gh-3420: crash if DML races with DDL.
+--
+fiber = require('fiber')
+
+-- turn off cache for error injection to work
+default_vinyl_cache = box.cfg.vinyl_cache
+box.cfg{vinyl_cache = 0}
+
+s = box.schema.space.create('test', {engine = 'vinyl'})
+_ = s:create_index('i1')
+_ = s:create_index('i2', {parts = {2, 'unsigned'}})
+_ = s:create_index('i3', {parts = {3, 'unsigned'}})
+_ = s:create_index('i4', {parts = {4, 'unsigned'}})
+for i = 1, 5 do s:replace({i, i, i, i}) end
+box.snapshot()
+
+test_run:cmd("setopt delimiter ';'")
+function async(f)
+    local ch = fiber.channel(1)
+    fiber.create(function()
+        local _, res = pcall(f)
+        ch:put(res)
+    end)
+    return ch
+end;
+test_run:cmd("setopt delimiter ''");
+
+-- Issue a few DML requests that require reading disk.
+-- Stall disk reads.
+errinj.set('ERRINJ_VY_READ_PAGE_TIMEOUT', 0.01)
+
+ch1 = async(function() s:insert({1, 1, 1, 1}) end)
+ch2 = async(function() s:replace({2, 3, 2, 3}) end)
+ch3 = async(function() s:update({3}, {{'+', 4, 1}}) end)
+ch4 = async(function() s:upsert({5, 5, 5, 5}, {{'+', 4, 1}}) end)
+
+-- Execute a DDL operation on the space.
+s.index.i4:drop()
+
+-- Resume the DML requests. Check that they have been aborted.
+errinj.set('ERRINJ_VY_READ_PAGE_TIMEOUT', 0)
+ch1:get()
+ch2:get()
+ch3:get()
+ch4:get()
+s:select()
+s:drop()
+
+box.cfg{vinyl_cache = default_vinyl_cache}
-- 
2.11.0